Re: [dpdk-dev] [PATCH 2/2] build: find max lcore programmatically

[Jerin Jacob <jerinjacobk@gmail.com>]

On Wed, Aug 26, 2020 at 2:44 AM Dharmik Thakkar <dharmik.thakkar@arm.com> wrote:
>
> For Arm, RTE_MAX_LCORE is hard-coded into the config. It leads to incorrect
> RTE_MAX_LCORE when machines have same Implemener and part number
> but different number of CPUs.
> For x86, RTE_MAX_LCORE is always set to 128 (using the value
> set in meson_options.txt)
>
> Use python script to find max lcore when using native build to
> correctly set RTE_MAX_LCORE.

We may need to build on the native arm64 machine and use it on another
arm64 machine(Just like x86).
So I think, at least for default config(which will be used by
distribution) to support max
lcores as fixed. I am not sure this patch changes those aspects or
not? Please check.

>
> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
>  config/get_max_lcores.py | 13 +++++++++++++
>  config/meson.build       | 13 ++++++++++++-
>  2 files changed, 25 insertions(+), 1 deletion(-)
>  create mode 100755 config/get_max_lcores.py
>
> diff --git a/config/get_max_lcores.py b/config/get_max_lcores.py
> new file mode 100755
> index 000000000000..ebf1c7efdadd
> --- /dev/null
> +++ b/config/get_max_lcores.py
> @@ -0,0 +1,13 @@
> +#!/usr/bin/python3
> +# SPDX-License-Identifier: BSD-3-Clause
> +# Copyright(c) 2020 Arm Limited
> +
> +import os
> +
> +max_lcores = []
> +
> +nCPU = os.cpu_count()
> +
> +max_lcores.append(str(nCPU & 0xFFF))             # Number of CPUs
> +
> +print(' '.join(max_lcores))
> diff --git a/config/meson.build b/config/meson.build
> index 6996e5cbeaa5..80c05bc15d2f 100644
> --- a/config/meson.build
> +++ b/config/meson.build
> @@ -237,11 +237,22 @@ else # for 32-bit we need smaller reserved memory areas
>         dpdk_conf.set('RTE_MAX_MEM_MB', 2048)
>  endif
>
> -
>  compile_time_cpuflags = []
>  subdir(arch_subdir)
>  dpdk_conf.set('RTE_COMPILE_TIME_CPUFLAGS', ','.join(compile_time_cpuflags))
>
> +# set max lcores
> +if machine != 'default' and not meson.is_cross_build()
> +       # The script returns max lcores
> +       params = files('get_max_lcores.py')
> +       cmd_out = run_command(params)
> +       if cmd_out.returncode() == 0
> +               cmd_lcore = cmd_out.stdout().to_lower().strip().split(' ')
> +       endif
> +       max_lcore = cmd_lcore[0].to_int()
> +       dpdk_conf.set('RTE_MAX_LCORE', max_lcore)
> +endif
> +
>  # set the install path for the drivers
>  dpdk_conf.set_quoted('RTE_EAL_PMD_PATH', eal_pmd_path)
>
> --
> 2.17.1
>